Power source for burst operation

ABSTRACT

A system, an electrical combination and a method for powering a load device. The combination may include a burst circuit configured to provide power to the load device to perform a burst operation, the burst circuit including a supercapacitor, a first switch between a power source and the supercapacitor and operable to control whether power is provided from the power source to charge the supercapacitor, and a second switch between the supercapacitor and the load device and operable to control whether power is provided from the supercapacitor to the load device; and an electronic processor configured to control the first switch and the second switch based at least in part on a voltage of the supercapacitor.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/752,758, filed Jan. 27, 2020, now U.S. Pat. No. 11,152,805, which isa continuation of U.S. patent application Ser. No. 16/591,224, filedOct. 2, 2019, now U.S. Pat. No. 11,043,828, which is a continuation ofU.S. patent application Ser. No. 15/849,763, filed Dec. 21, 2017, nowU.S. Pat. No. 10,491,020, which claims the benefit of priority to U.S.Provisional Application No. 62/438,098, filed Dec. 22, 2016, the entirecontent of each of which is hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to power sources and, more specifically,to power sources that provide burst operation.

SUMMARY

Fastener drivers are used to drive fasteners (e.g., nails, staples,tacks, etc.) into a work piece. These fastener drivers operate throughvarious means (e.g. compressed air, gas, powder, electrical energy, aflywheel mechanism, etc.) to provide a burst of power to drive thefastener into the work piece. However, these designs often have power,size, and cost constraints.

In one independent aspect, a battery-powered fastener driver may includea burst circuit with a supercapacitor for providing power to a motor ofthe fastener driver.

In another independent aspect, a battery pack may include battery cellswith different characteristics. The battery cells may be of differentphysical size (e.g., different diameter, different length, etc.), shape(e.g., cylindrical, prismatic, etc.), chemistry (e.g., differentlithium-based or other chemistries), operational characteristics (e.g.,Ampere-hour (Ah) capacity, temperature performance, nominal voltage,etc.), combinations thereof.

In yet another independent aspect, a battery charger may execute amethod of monitoring a health of a battery pack by determining directcurrent (DC) internal resistance of the battery pack based on amonitored voltage of the battery pack.

In a further independent aspect, a battery pack may include batterycells coupled by laser welding conductive straps to terminals of thebattery cells.

In another independent aspect, an electrical combination for powering aload device may be provided. The electrical combination may generallyinclude a burst circuit configured to provide power to the load deviceto perform a burst operation, the burst circuit including asupercapacitor, a first switch between a power source and thesupercapacitor and operable to control whether power is provided fromthe power source to charge the supercapacitor, and a second switchbetween the supercapacitor and the load device and operable to controlwhether power is provided from the supercapacitor to the load device;and an electronic processor configured to control the first switch andthe second switch based at least in part on a voltage of thesupercapacitor.

In yet another independent aspect, a method of powering a burstoperation of a load device may be provided. The method may generallyinclude determining, with an electronic processor, that a voltage of asupercapacitor is greater than or equal to a burst voltage threshold;controlling, with the electronic processor and in response todetermining that the voltage of the supercapacitor is greater than orequal to the burst voltage threshold, a first switch to open to preventpower from being provided by a power source to the supercapacitor, thefirst switch being between the power source and the supercapacitor;determining, with the electronic processor, that an actuator of the loaddevice has been actuated; and controlling, with the electronic processorand in response to determining that the actuator has been actuated, asecond switch to close to allow power to be provided from thesupercapacitor to the load device to perform the burst operation, thesecond switch being between the supercapacitor and the load device.

In a further independent aspect, a battery pack may generally include ahousing; a plurality of battery cells supported in the housing, theplurality of battery cells including a first battery cell having a firstcharacteristic and a second battery cell having a second characteristicdifferent than the first characteristic, the first characteristic andthe second characteristic being at least one of a physical size, ashape, a chemistry, and an operational characteristic; and a terminalelectrically connected to the first battery cell and the second batterycell.

Other independent aspects of the invention may become apparent byconsideration of the detailed description, claims and accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a battery-powered device, such as anailer for driving nails into a work piece.

FIG. 2 is a partial cross-sectional view of a portion of the device ofFIG. 1.

FIG. 3A is a block diagram of the device of FIGS. 1-2.

FIG. 3B is a circuit diagram of a portion of the device of FIGS. 1-2according to one exemplary embodiment.

FIGS. 4A-4B are flowcharts of a method of powering burst operations ofthe device of FIGS. 1-2 using supercapacitors within the device.

FIG. 5 is a block diagram of a separate burst device according to oneexemplary embodiment.

FIGS. 6A-6B are views of an alternate embodiment of a battery pack usedto power the device of FIGS. 1-2.

FIG. 7A is a cut-away view of another battery pack including twodifferent size battery cells.

FIG. 7B is a side view of yet another battery pack that also includestwo different size battery cells.

FIG. 7C is a circuit diagram of the battery cells of the battery pack ofFIG. 7A.

FIG. 8 is a block diagram of conductive straps electrically coupling afuse between battery cells according to one exemplary embodiment.

FIGS. 9A-9C illustrate exemplary geometries of laser welding patternsaccording to some embodiments.

FIG. 10 is a perspective view of a charger, for example, for chargingthe battery packs of FIGS. 6A, 6B, and 7.

FIG. 11 is a block diagram of the charger of FIG. 10.

FIG. 12 is a flowchart of a method performed by the charger of FIGS. 10and 11 of monitoring direct current (DC) internal resistance of abattery pack coupled to the charger.

FIG. 13 is a graph showing exemplary results of the method of FIG. 12being executed by the charger of FIGS. 10 and 11.

DETAILED DESCRIPTION

Before any independent embodiments of the application are explained indetail, it is to be understood that the application is not limited tothe details of construction and the arrangement of components set forthin the following description or illustrated in the following drawings.The application is capable of other independent embodiments and of beingpracticed or of being carried out in various ways. Also, it is to beunderstood that the phraseology and terminology used herein is for thepurpose of description and should not be regarded as limiting.

Use of “including” and “comprising” and variations thereof as usedherein is meant to encompass the items listed thereafter and equivalentsthereof as well as additional items. Use of “consisting of” andvariations thereof as used herein is meant to encompass only the itemslisted thereafter and equivalents thereof. Unless specified or limitedotherwise, the terms “mounted,” “connected,” “supported,” and “coupled”and variations thereof are used broadly and encompass both direct andindirect mountings, connections, supports, and couplings.

Also, the functionality described herein as being performed by onecomponent may be performed by multiple components in a distributedmanner. Likewise, functionality performed by multiple components may beconsolidated and performed by a single component. Similarly, a componentdescribed as performing particular functionality may also performadditional functionality not described herein. For example, a device orstructure that is “configured” in a certain way is configured in atleast that way but may also be configured in ways that are not listed.

Furthermore, some embodiments described herein may include one or moreelectronic processors configured to perform the described functionalityby executing instructions stored in non-transitory, computer-readablemedium. Similarly, embodiments described herein may be implemented asnon-transitory, computer-readable medium storing instructions executableby one or more electronic processors to perform the describedfunctionality. As used in the present application, “non-transitorycomputer-readable medium” comprises all computer-readable media but doesnot consist of a transitory, propagating signal. Accordingly,non-transitory computer-readable medium may include, for example, a harddisk, a CD-ROM, an optical storage device, a magnetic storage device, aROM (Read Only Memory), a RAM (Random Access Memory), register memory, aprocessor cache, or any combination thereof.

Many of the modules and logical structures described are capable ofbeing implemented in software executed by a microprocessor or a similardevice or of being implemented in hardware using a variety of componentsincluding, for example, application specific integrated circuits(“ASICs”). Terms like “controller” and “module” may include or refer toboth hardware and/or software. Capitalized terms conform to commonpractices and help correlate the description with the coding examples,equations, and/or drawings. However, no specific meaning is implied orshould be inferred simply due to the use of capitalization. Thus, theclaims should not be limited to the specific examples or terminology orto any specific hardware or software implementation or combination ofsoftware or hardware.

FIGS. 1-2 illustrate a battery-powered device 10 (i.e., a load device),such as, for example, a nailer that uses “burst operation” to drivenails into a work piece. In other constructions (not shown), the device10 may include another fastener-driving device, such as a stapler, todrive staples, tacks, etc., or other power tools that use burstoperation. In still other constructions (see, e.g., FIG. 5), the device10 may include another powered device using a burst of power to supply aload, such as a jump starter used to start a vehicle engine.

In the illustrated construction, the device 10 is powered by aremovable, rechargeable battery pack 14, such as a power tool batterypack. Alternatively, rechargeable battery cells (not shown) may bepermanently housed within and non-removable from the device 10.

The nailing device 10 includes an onboard drive mechanism 18. In theillustrated construction, the drive mechanism 18 includes a gas-springdrive mechanism. In other constructions (not shown), the nailing device10 may include another type of onboard drive mechanism, such as an aircompressor, a vacuum pump, a mechanical energy storage element (e.g., acoil spring), etc.

The device 10 generally includes a housing 20 connectable to andoperable to support the battery pack 14 and supporting the drivemechanism 18. An electric motor 22 (FIG. 1) is supported by the housing20 and operable to drive the drive mechanism 18. Fasteners are supportedin a magazine 24.

The gas spring-powered drive mechanism 18 includes a cylinder 26 and amovable piston 30 positioned within the cylinder 26 (FIG. 2). A driverblade 34 is attached to and movable with the piston 30. The drivemechanism 18 does not require an external source of air pressure but,rather, includes a storage chamber cylinder 38 of pressurized gas influid communication with the cylinder 26. In the illustrated embodiment,the cylinder 26 and movable piston 30 are positioned within the storagechamber cylinder 38.

With reference to FIG. 2, during a driving cycle, the driver blade 34and the piston 30 are movable between a ready position (i.e., top deadcenter; see FIG. 2) and a driven position (i.e., bottom dead center; notshown). A lifting assembly 42, which is powered by the motor 22, isoperable to move the driver blade 34 from the driven position to theready position.

In operation, the lifting assembly 42 drives the piston 30 and thedriver blade 34 to the ready position by energizing the motor 22. As thepiston 30 and the driver blade 34 are driven to the ready position, thegas above the piston 30 and the gas within the storage chamber cylinder38 is compressed. Once in the ready position, the piston 30 and thedriver blade 34 are held in position until released by user activationof a trigger 46.

When released, the compressed gas above the piston 30 and within thestorage chamber 38 drives the piston 30 and the driver blade 34 to thedriven position, thereby driving a fastener into a workpiece. Theillustrated drive mechanism 18 therefore operates on a gas springprinciple utilizing the lifting assembly 42 and the piston 30 to furthercompress the gas within the cylinder 26 and the storage chamber cylinder38.

In other constructions, on actuation of the trigger 46, a full drivingcycle may be completed. More specifically, when the user actuates thetrigger 46, the motor 22 is powered to cause the lifting assembly 42 tolift the piston 30 and the driver blade 34 and compress the gas. Uponreaching the ready position, the piston 30 and the driver blade 34 areimmediately released to drive the fastener.

The structure and operation of the device 10 and the drive mechanism 18may be similar to that disclosed in U.S. Patent Application PublicationNo. US 2016/022904 A1, published Aug. 11, 2016, the entire contents ofwhich is hereby incorporated by reference.

When driving a nail into a work piece, the motor 22 is energized for ashort period of time to cause the drive mechanism 18 to drive a nail andis de-energized until another nail is to be driven into the work piece.The operation of the device 10 may thus be referred to as a “burstoperation” in which power is supplied (e.g., the motor 22 is energized)for short periods of time. For example, when the device 10 is used todrive twenty nails into a work piece over a one minute period, the motor22 may be energized twenty times in bursts of one second or less (e.g.,from about 0.05 seconds to about 0.10 seconds) to drive each nail intothe work piece.

FIG. 3A illustrates a block diagram of the device 10. The device 10includes an electronic processor 305 (for example, a microprocessor, orother electronic controller), a memory 310, an indicator (e.g., one ormore light-emitting diodes (LEDs) 315), and the motor 22.

The memory 310 may include read only memory (ROM), random access memory(RAM), other non-transitory computer-readable media, or a combinationthereof. The processor 305 is configured to receive instructions anddata from the memory 310 and execute, among other things, theinstructions. In particular, the processor 305 executes instructionsstored in the memory 310 to perform one or more methods describedherein. The processor 305 is also configured to control the LEDs 315(for example, to indicate an operating state of the device 10, acondition of the battery pack 14, a voltage of the supercapacitor(s)340, or the like) and receive electrical signals relating to the motor22 (for example, a speed of the motor 22 as detected by Hall sensorsand/or a current drawn by the motor 22 as detected by a current sensor).

The battery pack 14 provides power to the processor 305, the LEDs 315,and other control circuitry for the device 10. The battery pack 14 alsocharges the supercapacitor(s) 340 of a burst circuit 325, as explainedin greater detail below.

Due to high current requirements of a burst operation, the battery pack14 does not generally provide power for a burst operation (e.g., todrive a fastener into a work piece). For example, a burst operation ofthe device 10, such as the nailer, may require between approximately 100A and 120 A to power the motor 22 to cause the lifting assembly 42 tomove the piston 30 and the driver blade 34 to the ready position. Apartially-charged battery pack and/or a battery pack with increasedinternal resistance (due to numerous charge-discharge cycles, damage,etc.) may not be able to provide the current required to power a burstoperation.

Additionally, while a battery pack with sufficient charge and/or with aminimum internal resistance may be able to provide the necessary currentfor a burst operation, during such high current discharge, the voltageof the battery pack may decrease below the operating voltage of theprocessor 305 and other control circuitry. In such conditions, theprocessor 305 and the control circuitry may shut down, causing thedevice 10 to stop operating.

Accordingly, the device 10 is generally unable to operate or functionproperly when the battery pack 14 itself delivers the high current for aburst operation.

To provide the burst operation, the illustrated device 10 includes aburst circuit 325 for supplying a burst of power to the motor 22 (orother load). In some embodiments, the burst circuit 325 is locatedwithin the battery pack 14. In some constructions (such as theillustrated construction), the load (e.g., the motor 22) is poweredsolely by the burst circuit 325. In such constructions, battery cells ofthe battery pack 14 power the processor 305, the LEDs 315, and othercontrol circuitry during a burst operation. In some constructions wherethe burst circuit 325 is located within the battery pack 14, the batterypack 14 includes different sets of terminals to respectively providepower from the burst circuit 325 and the battery cells. In otherconstructions, the battery pack 14 provides power from the burst circuit325 and the battery cells through the same set of terminals and includesa switch to control whether the burst circuit 325 or the battery cellsprovide power (e.g., similar to the dual-powered device embodimentdescribed below).

As shown in FIG. 3A, the illustrated burst circuit 325 includes a firstswitch 330, a second switch 335, and one or more supercapacitor(s) 340.In some embodiments, the supercapacitors 340 are connected in parallel(see FIG. 3B). Although the supercapacitors 340 are described and shown(in FIG. 3B) in the plural form, in some embodiments, the burst circuit325 may include a single supercapacitor 340. It should also beunderstood that, in other embodiments (not shown), more than twosupercapacitors 340 may be provided.

The first switch 330 connects the battery pack 14 to thesupercapacitor(s) 340. The second switch 335 connects thesupercapacitor(s) 340 to the motor 22. In some embodiments, the firstswitch 330 and the second switch 335 are field-effect transistors (FETs)controlled by the processor 305. The processor 305 is configured tocontrol the state of the first switch 330 and the state of the secondswitch 335 to allow or inhibit current to flow through each switch.

In some embodiments, the processor 305 monitors a voltage of thesupercapacitor(s) 340. The processor 305 is also coupled to the batterypack 14 to monitor one or more characteristics of the battery pack 14(e.g., measure a voltage of the battery pack 14 and/or receiveinformation from the battery pack 14 indicative of a condition of thebattery pack 14). For example, the battery pack 14 may include anelectronic processor (not shown) communicating with the processor 305through a communication terminal (not shown). Alternatively, the batterypack 14 may include a terminal (not shown) allowing the processor 305 todetermine the temperature of the battery pack 14 (e.g., using athermistor (not shown) within the battery pack 14). In some embodiments,the processor 305 may also monitor one or more characteristics of theload 22.

FIG. 3B illustrates how the battery pack 14 electrically couples to thesupercapacitor(s) 340 and to the processor 305. As shown in FIG. 3B, thebattery pack 14 is connected in parallel with the supercapacitor(s) 340when the first switch 330 is closed. However, when the first switch 330is open, the battery pack 14 is not connected to the supercapacitor(s)340 and thus, current is unable to flow between the battery pack 14 andthe supercapacitor(s) 340.

The first switch 330 may be closed to charge the supercapacitor(s) 340using the battery pack 14. In some embodiments, the processor 305controls the first switch 330 using a PWM signal to charge thesupercapacitor(s) 340. For example, the PWM signal may begin with arelatively low duty cycle to prevent or limit high inrush current frombeing drawn by the supercapacitor(s) 340 having a low state of charge.As the voltage of the supercapacitor(s) 340 increases, the PWM dutycycle also increases until the supercapacitor(s) 340 are sufficientlycharged, as explained in more detail below. In alternate embodiments, aresistor (not shown) in series with the first switch 330 is used toprevent or limit high inrush current from being drawn by thesupercapacitor(s) 340.

In some embodiments, a boost converter (not shown) may be used whencharging the supercapacitor(s) 340. In such embodiments, the voltageoutput of the battery pack 14 is matched to the voltage input of thesupercapacitor(s) 340. The supercapacitor(s) 340 may thus be chargedwithout controlling the first switch 330 using the PWM signal describedabove, reducing the resulting switching losses that occur.

As shown in FIG. 3B, the state of the second switch 335 determineswhether the load 22 is connected to the supercapacitor(s) 340 (i.e.,whether the load 22 receives power from the supercapacitor(s) 340). Inthe illustrated construction, when power is supplied from thesupercapacitor(s) 340 to the load 22, the first switch 330 is placed(e.g., by the processor 305) in the open state to prevent feedbackcharging from the supercapacitor(s) 340 to the battery pack 14.

As shown in FIG. 3B, when the first switch 330 is open, the battery pack14 remains connected to the processor 305 and other control circuitry ofthe device 10. Accordingly, during a burst operation of the device 10,power is supplied from the supercapacitor(s) 340 to power the load 22(e.g., to power the motor to cause the drive mechanism 18 to drive anail into a work piece); meanwhile, the battery pack 14 powers theprocessor 305 and other control circuitry of the device 10. Such aconfiguration allows for sufficient (high) current to be supplied to theload 22 to power a burst operation without the processor 305 and othercontrol circuitry shutting down (e.g., because the voltage of thebattery pack 14 drops below the operating voltage of the processor 305and other control circuitry).

Similarly, in embodiments where the burst circuit 325 is located in thebattery pack 14, the battery cells of the battery pack 14 remainconnected to the processor 305 and other control circuitry of the device10 when the first switch 330 is open. Accordingly, during a burstoperation of the device 10, power is supplied from the supercapacitor(s)340 to power the load 22 (e.g., to power the motor to cause the drivemechanism 18 to drive a nail into a work piece); meanwhile, the batterycells of the battery pack 14 power the processor 305 and other controlcircuitry of the device 10. As mentioned above, such a configurationallows for sufficient (high) current to be supplied to the load 22 topower a burst operation without the processor 305 and other controlcircuitry shutting down. In some embodiments, the electronic processor305 that controls the switches 330 and 335 and monitors the voltage ofthe supercapacitor(s) 340 is located in the battery pack 14.

FIG. 4A illustrates a method 400 of powering burst operations from thesupercapacitor(s) 340. In some embodiments, including the illustratedembodiment, the method 400 is executed by the processor 305 of thedevice 10. At block 405, the device 10 is turned on. At block 410, theprocessor 305 opens the first switch 330 and the second switch 335 toprevent current from flowing to or from the supercapacitor(s) 340.

At block 415, the processor 305 determines whether the voltage of thebattery pack 14 is greater than a battery low voltage threshold. Whenthe voltage of the battery pack 14 is less than or equal to the batterylow voltage threshold, at block 420, the processor 305 indicates lowbattery voltage (e.g., flashes an LED) and shuts down the device 10. Insuch a circumstance, the voltage of the battery pack 14 is too low tooperate the device 10 (i.e., too low to charge the supercapacitor(s)340). The flashing LED may indicate to a user that the battery pack 14needs to be replaced or recharged.

When the voltage of the battery pack 14 is greater than the battery lowvoltage threshold, at block 425, the processor 305 determines whetherthe voltage of the supercapacitor(s) 340 is greater than or equal to aburst voltage threshold. In some embodiments, the burst voltagethreshold is indicative of whether the charge of the supercapacitor(s)340 is sufficient to power a burst operation of the device 10. When thevoltage of the supercapacitor(s) 340 is less than the burst voltagethreshold, the method 400 proceeds to a charging sub-method 460 of FIG.4B, explained in greater detail below.

When the voltage of the supercapacitor(s) 340 is greater than or equalto the burst voltage threshold, the processor 305 opens the first switch330 to prevent current flow between the battery pack 14 and thesupercapacitor(s) 340. At block 435, the processor 305 determineswhether the trigger 46 is pressed. When the trigger 46 is not pressed,the method 400 proceeds back to block 415 to continuously monitor thevoltage of the battery pack 14 and the voltage of the supercapacitor(s)340.

When the trigger 46 is pressed, at block 440, the processor 305 closesthe second switch 335 to allow current to flow to the motor 22 from thesupercapacitor(s) 340. This closing of the second switch 335 starts aburst operation of the device 10 to, in the illustrated construction,drive a nail into a work piece. In some embodiments, the processor 305controls the second switch 335 using a PWM signal during the burstoperation.

At block 445, the processor 305 may determine whether an operation ofthe device 10 has been completed (e.g., whether the nail has been driveninto a work piece by the device 10). If the operation has not beencompleted (e.g., if the fastener has not yet been fully driven into thework piece) and if further driving of the fastener is possible, themethod remains at block 445 until completion or until discharge of thesupercapacitor(s) 340 below the burst voltage threshold. If furtherdriving is not possible, the processor 305 may alert the user (e.g.,through the LEDs) of an incomplete or failed fastener driving operation.

When the operation has been completed, at block 450, the processor 305opens the second switch 335 to prevent current from flowing to the motor22 from the supercapacitor(s) 340, ending the burst operation.

After the second switch 335 is opened to end the burst operation atblock 450, the method 400 returns to block 415 to repeat the method 400.Repetition of the method 400 allows for numerous burst operations of thedevice 10 powered by the supercapacitor(s) 340. In between these burstoperations, the supercapacitor(s) 340 are charged by the battery pack 14when the voltage of the supercapacitor(s) 340 is below a threshold(e.g., the burst voltage threshold).

FIG. 4B illustrates the sub-method 460 for charging thesupercapacitor(s) 340. As explained above, at block 425 (see FIG. 4A),when the voltage of the supercapacitor(s) 340 is less than the burstvoltage threshold, the method 400 proceeds to the charging sub-method460 shown in FIG. 4B.

At block 465, the processor 305 determines whether the second switch 335is open to prevent current flow to the motor 22 from thesupercapacitor(s) 340. If the second switch 335 is closed, at block 470,the processor 305 opens the second switch 335 to prevent current flow tothe motor 22 from the supercapacitor(s) 340. The charging sub-method 460then proceeds to block 475. At block 465, when the second switch 335 isalready open, the charging sub-method 460 also proceeds to block 475.

At block 475, the processor 305 closes the first switch 330 to allowcurrent flow from the battery pack 14 to the supercapacitor(s) 340 tocharge the supercapacitor(s) 340. As explained above, in someembodiments, the processor 305 controls the first switch 330 using a PWMsignal to charge the supercapacitor(s) 340.

At block 480, the processor 305 determines whether the voltage of thesupercapacitor(s) 340 is greater than or equal to the burst voltagethreshold. When the voltage of the supercapacitor(s) 340 remains belowthe burst voltage threshold, at block 485, the processor 305 continuesto control the first switch 330 to allow current to flow from thebattery pack 14 to the supercapacitor(s) 340 to charge thesupercapacitor(s) 340. The charging sub-method 460 then returns to block480 to continue monitoring the voltage of the supercapacitor(s) 340.

When the voltage of the supercapacitor(s) 340 is greater than or equalto the burst voltage threshold, the method 400 returns to block 430 (seeFIG. 4A) to continue operation as described above. Thus, the method 400and the sub-method 460 allow the supercapacitor(s) 340 to power burstoperations of the device 10 and to be charged between burst operationsof the device 10. The battery pack 14 is used to charge thesupercapacitor(s) 340 between burst operations and to power theprocessor 305 and other control circuitry of the device 10 during andbetween burst operations.

In alternate embodiments, at block 435, a burst operation of the device10 occurs upon a monitored characteristic of the device 10 exceeding apredetermined threshold while, at other times, operational power isprovided by the battery pack 14. Such a device 10 is a dual-powereddevice—the load 22 is powered by the battery pack 14 and/or by thesupercapacitor(s) 340. For example, in some embodiments, the device 10may include a reciprocating saw, a circular saw, a drill, etc., (notshown) having a load sensor (not shown; e.g. a current sensor for themotor 22). The burst operation is provided to operate under an increasedload (e.g., the saw “bogging down” or binding on the work piece).

For most operations (e.g., “normal” operations), the battery pack 14 iscapable of supplying the required discharge current to power the load 22while maintaining sufficient voltage to also power the processor 305 andthe other control circuitry as necessary during operation. Under normaloperating conditions, the load 22 of the dual-powered device (e.g., thesaw, drill, etc.) is powered by the battery pack 14.

When the load sensor senses a load above a predetermined “burst load”threshold, the processor 305 may initiate a burst operation powered bythe supercapacitor(s) 340. In other words, the processor 305 maydisconnect the battery pack 14 from the load 22 and connect thesupercapacitor(s) 340 to the load 22 to provide a burst of power.

When the load sensor senses that the load is below a “normal load”threshold, the processor 305 may re-initiate “normal” operations of theload 22 powered of the battery pack 14. The processor 305 may disconnectthe supercapacitor(s) 340 from the load 22 and connect the battery pack14 to the load 22 to provide “normal” power.

FIG. 5 illustrates a block diagram of a burst device 500 (or burstadapter) including a burst circuit 505 (similar to the burst circuit325) to provide power to an external load (e.g., a burst-receivingdevice 535). Such a burst device 500 may be a jumpstarting device forjumpstarting a vehicle battery. Alternatively, the burst device 500 takethe form of an “adapter” configured to receive a battery pack (such asthe battery pack 14) and separate from and connectable (e.g., at leastelectrically) to a load (e.g., a fastener-driving device (as disclosedin U.S. Patent Application Publication No. US 2016/022904 A1), anotherpower tool, a non-motorized device, etc.) to provide burst power to aload.

In some embodiments, the burst device 500 is integrated into the batterypack 14. In other words, the battery pack 14 may include a burst circuit505 that functions in a similar manner as the burst device 500 describedbelow. In some embodiments, the electronic processor 525 that controlsthe switches 540 and 545 and monitors the voltage of thesupercapacitor(s) 530 is located in a device outside of the burst device500 (e.g., in the burst receiving device 535, in the battery pack 14, orthe like).

The separate burst device 500 allows the supercapacitor(s) 530 of theburst circuit 505 to provide power to loads/devices that do not includea burst circuit 505, 325. In some embodiments (e.g., when the burstdevice 500 is a jump starting device for a vehicle battery), the burstdevice 500 is capable of providing between approximately 300 Amps and600 Amps (or more depending on the number and characteristics of thesupercapacitor(s) 530) to the burst-receiving device 535.

As shown in FIG. 5, the burst device 500 includes a housing 502 defininga battery connection portion 503 (e.g., a terminal block and a batterysupport) for electrical and/or mechanical connection to the battery pack14 and a load connection portion 504 (e.g., a terminal block and asupport) for electrical and/or mechanical connection to the load. Thehousing 502 supports a burst circuit 505, an actuator 510 (e.g., abutton, a trigger, a signal-receiving unit, etc.), a memory 515, anindicator (e.g., one or more LEDs 520), and an electronic processor 525.These components are similar to the corresponding components describedabove with respect to the device 10 (see FIG. 3).

In the burst device 500, the processor 525 may monitor the actuator 510to initiate a burst of power from supercapacitor(s) 530 to theburst-receiving device 535. The processor 525 may also control the LEDs520 to indicate a status of the burst device 500 (for example, whetherthe supercapacitor(s) 530 are charged and capable of providing a burstof power), the battery pack 14 and/or the burst-receiving device 535.

Generally, the processor 525 controls operation of the burst circuit 505in a similar manner to the operation of the burst circuit 325 of thedevice 10. For example, the processor 525 may execute the method 400 ofFIG. 4A to provide one or more bursts of power from thesupercapacitor(s) 530 to the load (the burst-receiving device 535)electrically coupled to the burst device 500.

The processor 525 may also execute the charging sub-method 460 of FIG.4B to charge the supercapacitor(s) 530 using the battery pack 14electrically coupled to the burst device 500. The processor 525 controlscharging and discharging of the supercapacitor(s) 530 by controlling thefirst switch 540 and the second switch 545 in a similar manner to thatof the burst circuit 325 of the device 10.

FIGS. 6A-6B illustrate a battery pack 600 including a number of firstbattery cells 602 (e.g., three; illustrated as being arranged verticallyin a stem 605 of a housing of the battery pack 600) and a number ofdifferent second battery cells 604 (e.g., three; illustrated as beingarranged horizontally in a base 610 of a housing of the battery pack600). In some embodiments, the battery pack 600 operates in a similarmanner as described above with respect to battery pack 14 and may beused to power the device 10. In some embodiments, the stem 605 isinserted into a battery receptacle (not shown) of a power tool (forexample, the device 10). In such embodiments, the base 610 generallyremains external to a housing (not shown) of the power tool.

The battery cells 602, 604 may be connected in any combination with eachother to provide desired voltage and current outputs for a desiredapplication. For example, in some embodiments, two battery cells 602 inthe stem 605 are connected in parallel, two battery cells 604 in thebase 610 are connected in parallel, and one battery cell 602 in the stem605 and one battery cell 604 in the base 610 are connected in parallel.In such an exemplary configuration, the three sets of parallel batterycells 602, 604 may be connected in series. In some embodiments, thebattery cells 602, 604 are “18650” (18 mm in diameter by 65 mm inlength) lithium-ion batteries.

In some embodiments, larger-sized battery cells (e.g., “26700” (26 mm by70 mm) cells or “21700” (21 mm by 70 mm) cells compared to 18650 cells)may be used to provide increased ampere-hour capacity of a battery pack.Due to size constraints of the battery receptacle of the associatedpower tools, use of larger-sized battery cells in the stem 605 of thebattery pack 600 may be limited. Specifically, increasing the size ofthe stem 605 to accommodate larger-sized battery cells would requireincreasing the size of the battery receptacle of the power tools toreceive such a larger stem. However, use of larger-sized battery cellsin the base 610 of the battery pack 600 would not generally requiremodification of the battery receptacle of power tools as the base 610remains external to the power tool when the battery pack 600 isinserted.

FIG. 7A illustrates a cut-away view of a battery pack 705 includingdifferent types of battery cells (i.e., battery cells that include oneor more different characteristics than each other). The battery cellsmay be of different physical size (e.g., different diameter, differentlength, etc.; see FIG. 7A), shape (e.g., cylindrical, prismatic, etc.),chemistry (e.g., different lithium-based or other chemistries),operational characteristics (e.g., Ampere-hour (Ah) capacity,temperature performance, nominal voltage, etc.), combinations thereof.In some embodiments, the battery pack 705 operates in a similar manneras described above with respect to the battery pack 14 and may be usedto power the device 10.

Similar to the battery pack 600 shown in FIGS. 6A and 6B, the batterypack 705 includes a stem 710 and a base 715. The stem 710 houses anumber of smaller-sized battery cells 720 (for example, three 18650lithium-ion battery cells). The base 715 houses a number of larger-sizedbattery cells 725 (for example, three 21700 lithium-ion battery cells).In some embodiments (as illustrated), the battery cells 720, 725 havedifferent diameters and different lengths (18650 compared to 21700; asshown in FIG. 7A). In other embodiments (not shown), the battery cells720, 725 have only different diameters (18 mm compared to 21 mm) ordifferent lengths (65 mm compared to 70 mm).

As mentioned above, in some embodiments, the battery cells 720, 725 havedifferent operational characteristics (e.g., Ampere-hour (Ah) capacity,temperature performance, nominal voltage, etc.). For example, thebattery cells 720, 725 may have different ampere-hour capacities. Asillustrated, the larger-sized battery cells 725 (e.g., the 21700 cells)have a greater ampere-hour capacity than the smaller-sized battery cells720 (e.g., the 18650 cells).

As another example, the battery cells 720, 725 may have differenttemperature performance characteristics (e.g., one set of battery cellsmay have a wider range of temperatures in which it may properly functionor one set of battery cells may function better at low temperatures orhigh temperatures). The battery controller (not shown) may determine,based on the conditions (e.g., ambient and/or operational conditions),which battery cells 720, 725 to use to supply power.

In some embodiments, each smaller-sized battery cell 720 in the stem 710is connected in parallel with one larger-sized battery cell 725 in thebase 715. In alternate embodiments, multiple smaller-sized battery cells720 may be connected in parallel with multiple larger-sized batterycells 725. The parallel combinations of battery cells 720 and 725 may beconnected in any series combination with each other to provide desiredvoltage and current outputs for a desired application.

Although FIG. 7A shows the battery pack 705 as including six batterycells, in some embodiments, the battery pack 705 includes more or fewerbattery cells that may be connected in a similar manner to the batterycells 720, 725. For example, FIG. 7B illustrates a battery pack 730including eight larger battery cells 735 and eight smaller battery cells740 in a base 745 of the battery pack 730. As shown in FIG. 7B, thesmaller battery cells 740 may be positioned between rows of largerbattery cells 735 and/or along a bottom of the base 745. Using batterycells of different sizes allows for space within the base 745 to beoptimized to make the battery pack 730 less bulky and easier tomanipulate.

The configuration of the battery cells 735 and 740 in FIG. 7B is merelyexemplary and other configurations may be used. Although not shown inFIG. 7B, in some embodiments, a stem 750 of the battery pack 730 alsoincludes battery cells, as previously explained with respect to FIGS.6A, 6B, and 7A. In alternate embodiments (not shown), the stem 750includes cylindrically-shaped battery cells, and the base 745 includesprismatic battery cells.

In some embodiments, the battery cells 720, 725 and the battery cells735, 740 are coupled to each other by laser welding conductive straps toterminals of the battery cells, as explained in greater detail below.

Although several configurations of connections between the battery cells720, 725 have been explained, the operation of the battery cells 720,725 will be described with respect to the configuration that includesthree parallel combinations of a smaller-sized battery cell 720 and alarger-sized battery cell 725. These three parallel combinations may beconnected in series to provide a desired voltage (for example,approximately 12V) at the terminals of the battery pack 705. FIG. 7Cillustrates a circuit diagram of the battery cells 720, 725 in such anexemplary configuration.

In the illustrated configuration, the total ampere-hour capacity of thebattery pack 705 is the sum of the capacities of one smaller-sizedbattery cell 720 and one larger-sized battery cell 725. Accordingly, thetotal ampere-hour capacity of the illustrated battery pack 705 isincreased compared to a battery pack including only six smaller-sizedbattery cells 720.

Despite the different characteristics of the battery cells 720, 725, asdescribed above, in some embodiments, the battery cells 720, 725 havesubstantially the same nominal voltage. Within each parallel combinationof a smaller-sized battery cell 720 and a larger-sized battery cell 725,the battery cells 720, 725 balance each other despite having differentampere-hour capacities because they have the same voltage. Thus,existing charging, discharging, and balancing methods of battery packsincluding battery cells of the same size and ampere-hour capacity maystill be used with the battery pack 705 having different size andampere-hour capacity battery cells 720, 725 (for example, to monitor andcontrol charging and discharging of the battery pack 705).

Within each parallel combination of a smaller-sized battery cell 720 anda larger-sized battery cell 725, the larger-sized battery cell 725 has ahigher impedance and a higher energy than the smaller-sized battery cell720. Accordingly, the larger-sized battery cells 725 are referred to asenergy cells while the smaller-sized battery cells 720 are referred toas low impedance cells.

With reference to FIG. 7C, in some embodiments, the battery pack 705 mayinclude switches to disconnect either the battery cells 720 or thebattery cells 725 depending on monitored characteristics of the batterypack 705. In such embodiments, the battery pack 705 provides powersolely from a single type of battery cell intended to operate under themonitored characteristic (e.g., low temperature).

For example, when the battery cells 720 and 725 include differenttemperature characteristics, an electronic processor of the battery pack705 may disconnect either the battery cells 720 or 725 based on amonitored temperature (e.g., ambient and/or of the battery pack 705).For example, when the battery pack 705 is in a cold environment (e.g.,temperature less than a desired operating temperature for one set ofbattery cells 720 or 725), the processor may disconnect such batterycells. In such embodiments, the battery pack 705 provides power solelyfrom the battery cells 720 or 725 intended to operate at lowertemperatures (e.g., having a low temperature characteristic compared tothe other cells).

In some embodiments, the battery pack 14, 600 and 705 includes anelectronic processor (not shown) and a memory (not shown) that may besimilar to the processor 305 and the memory 310 described above withrespect to the nailing device 10 (see FIG. 3A). The battery pack 14, 600and 705 may also include at least one sensor for monitoring anoperational characteristic of the battery packs 14, 600, and 705 duringoperation.

For example, the battery pack 14, 600 and 705 may include a currentsensor for monitoring a current provided by the battery pack 14, 600 and705. In some embodiments, the processor of the battery pack 14, 600 and705 may monitor an amount of time that the battery pack 14, 600 and 705provide current to a device.

In some embodiments, the battery pack 14, 600, and 705 determines a typeof device to which the battery pack 14, 600,and 705 is connected. Insuch embodiments, the processor of the battery pack 14, 600 and 705 maymake such a determination by communicating with the processor 305 of thenailing device 10 or other device.

The memory of the battery pack 14, 600 and 705 may store monitoredoperational characteristics of the battery pack 14, 600 and 705. Thememory of the battery pack 14, 600 and 705 may also store the type ofdevice to which the battery pack 14, 600 and 705 is or was connected.Based on this information, the battery pack 14, 600 and 705 may provideinformation to a user to improve operation of the battery pack 14, 600and 705.

For example, the battery pack 14, 600 and 705 may include a wirelesscommunication controller to communicate with an external device (e.g., asmart phone). In such embodiments, the wireless communication controllerand the external device may be similar to those disclosed in U.S. PatentApplication Publication No. 2016/0342151, filed May 16, 2016, the entirecontents of which is hereby incorporated by reference.

The battery pack 14, 600 and 705 may communicate with the externaldevice to provide usage data of the battery pack 14, 600 and 705 (e.g.,a type of device that the battery pack has been used to power in thepast and operational characteristics of the battery pack 14, 600 and 705during discharge) and predicted intended future operation of the batterypack 14, 600 and 705.

For example, when the battery pack 14, 600 and 705 is not suitable tothe device or power tool to which it is connected, the battery pack 14,600, and 705 may communicate with the external device to recommend anappropriate battery pack be used in place of the battery pack 14, 600and 705 in future operations with device or power tool. In turn, theexternal device may communicate this information to the user (e.g.,display this recommendation such that it is viewable by a user).

More specifically, when a low-capacity, discharged and/or damagedbattery pack 14, 600 and 705 is connected to a high-demand power tool,the battery pack 14, 600, and 705 may communicate with the externaldevice and/or to the user to recommend that a higher-capacity,fully-charged and/or new battery pack be used in place of the batterypack 14, 600 and 705 in future operations with the high-demand powertool.

Such a recommendation may extend the useful life of the battery pack 14,600 and 705 by informing the user that a different battery pack wouldlast longer than the battery pack 14, 600, and 705 when used with thehigh-demand power tool. Such a recommendation may also improve thefunctionality of the high-demand power tool by informing the user that ahigher-capacity battery pack is better suited to power the high-demandpower tool. In some embodiments, a specific alternate battery pack maybe recommended based on the type of device being operated by the user.

As mentioned above, in some embodiments, the battery cells (e.g., thebattery cells 602, 604 and/or the battery cells 720, 725) areelectrically coupled by laser welding conductive straps to terminals ofthe battery cells. Laser welding allows dissimilar metals that may notbe capable of being welded together using resistance welding to bewelded together. Compared to resistance welding, laser welding mayincrease pull strength between objects that are welded together.Additionally, laser welding allows for softer metals to be weldedtogether than resistance welding allows.

FIG. 8 illustrates conductive straps 805 electrically coupling a fuse810 between battery cells 815 at laser welds 820. In some embodiments,the conductive straps 805 are made of aluminum or copper and arelaser-welded to a stainless steel battery terminal of the battery cells815. The conductive straps 805 are also laser welded to aluminum orcopper terminals of the fuse 810. In such embodiments, the conductivestraps 805 and the terminals of the fuse 810 may also be made ofdissimilar metals (e.g., conductive straps 805 made of aluminum andterminals of the fuse 810 made of copper or vice versa). In alternateembodiments, the conductive straps 805 may be made of copper with tin orwith cladding layers of at least two materials of the group consistingof copper, stainless steel, and nickel.

In some embodiments, laser welding may allow battery cells withterminals made of dissimilar metals to be welded together. For example,cylindrical battery cells with battery terminals made of a first metaland prismatic battery cells with battery terminals made of a secondmetal may be electrically coupled by laser welding.

As mentioned above, compared to resistance welding, laser welding mayincrease pull strength between objects that are welded together (e.g.,the conductive straps 805 and the battery cells 815). Differentgeometries of laser welding patterns may increase the pull strengthbetween welded objects.

FIGS. 9A-9C illustrate exemplary geometries of laser welding patternsused to weld conductive straps 805, fuses 810, and/or battery cells 815together. FIG. 9A shows a conductive strap 805 laser welded between theterminals of two battery cells 815 using a flower geometry pattern 905.As shown in FIG. 9A, the illustrated flower geometry pattern 905includes six spot welds that surround a single spot weld. However, inalternate embodiments (not shown), more or fewer spot welds surround thecentral spot weld.

FIG. 9B shows a target geometry pattern 910 with a spot weld surroundedby a circular weld. In some embodiments, the circular weld is completedusing overlapping loops as shown by loop pattern 912 in part of thecircular weld of FIG. 9B. In alternate embodiments, additional spotwelds may be included inside the circular weld. In some embodiments, thecircular weld may surround the flower geometry pattern 905 shown in FIG.9A.

FIG. 9C shows a spiral geometry pattern 915. In some embodiments, thespiral geometry pattern 915 may be surrounded by the circular weld ofFIG. 9B. The laser welding geometry patterns 905, 910 and 915 shown inFIGS. 9A-9C are merely exemplary. Additional laser welding geometrypatterns may be used in alternate embodiments.

Laser welding may increase the overall pull strength by increasing thepull strength in at least one direction compared to resistance welding.For example, the generally circular shape of the geometry patterns 905,910 and 915 shown in FIGS. 9A-9C provide similar pull strength in alldirections. In contrast, resistance-welding patterns generally includeonly straight line welds in one or two directions and do not providesimilar pull strength in all directions.

When the battery packs 14, 600 and 705 are depleted, a charger 1005 (seeFIG. 10) may be used to recharge the battery packs 14, 600 and 705.Although the below explanation of the charger 1005 refers to charging ofthe battery pack 14, the same concepts and methods apply to charging thebattery packs 600 and 705 and to other battery packs (not shown).

As shown in FIG. 10, the charger 1005 includes a power cord 1010 forconnecting to a power source (e.g., a wall outlet for AC power) toprovide power to the charger 1005. The charger 1005 also includes one ormore battery pack receptacles 1015 (two shown) for receiving batterypacks. One receptacle 1015a is configured to receive the battery pack 14(for example, the stem of the battery pack 14 inserted into thereceptacle 1015a) while the other receptacle 1015b is configured toreceive battery packs of an alternate shape (e.g., a slide-on batterypack).

FIG. 11 illustrates a block diagram of the charger 1005. In someembodiments, the charger 1005 includes some similar components as thedevice 10. For example, the charger 1005 includes an electronicprocessor 1105, a memory 1110, and an indicator (e.g., LEDs 1115). Thesecomponents may have similar functionality to the correspondingcomponents described above with respect to the device 10 (see FIG. 3A).

The charger 1005 also includes an AC/DC converter and other conditioningcircuitry 1120 and a charging control switch 1125. In some embodiments,the charging control switch 1125 includes a FET controlled by theprocessor 1105. For example, when the charging control switch 1125 isclosed, current flows from an alternating current (AC) power source 1128through the AC/DC converter and other conditioning circuitry 1120 tocharge the battery pack 14. In some embodiments, the processor 1105controls the charging control switch 1125 using a PWM signal.

The charger 1005 also includes a load bank 1130 and a load bank switch1135. The load bank switch 1135 is controlled by the processor 1105 toconnect the battery pack 14 to one or more testing loads instead of tothe AC/DC converter and other conditioning circuitry 1120 and the ACpower source 1128. While FIG. 11 shows a single load bank switch 1135,in some embodiments, the charger 1005 includes multiple load bankswitches.

In some embodiments, the processor 1105 executes a method of monitoringbattery health by determining a DC internal resistance of the batterypack 14. The DC internal resistance of a battery pack is indicative ofthe health of the battery pack. As a battery pack ages, the DC internalresistance tends to increase which, in turn, decreases performance ofthe battery pack.

The DC internal resistance affects the capacity of the battery pack—thehigher the DC internal resistance of a battery pack, the higher thelosses while charging and discharging the battery pack. These lossesincrease as the charging current or discharging current increase. Inother words, the higher the discharge rate of a battery pack, the lowerthe available capacity of the battery pack.

In some embodiments, the DC internal resistance of the battery pack 14is determined by the battery charger 1005 by monitoring the voltage ofthe battery pack 14 as a load connected to the battery pack 14 isvaried. As the load connected to the battery pack 14 varies, the voltageof the battery pack 14 will also vary. From the monitored changes involtage of the battery pack 14 as the load varies, the DC internalresistance of the battery pack 14, which, again, is indicative of thehealth of the battery pack 14, is determined.

FIG. 12 illustrates an exemplary method 1200 of monitoring the DCinternal resistance of the battery pack 14. At block 1205, the processor1105 opens the charging control switch 1125 to ensure that the batterypack 14 is disconnected from the charging power source 1128. At block1210, the processor 1105 controls the load bank switch 1135 to connectthe battery pack 14 to a first load of the load bank 1130 such that thebattery pack 14 applies a first discharge current (e.g., ten amps). Thebattery pack 14 remains connected to this load for a time period (e.g.,five seconds). During this time, the processor 1105 monitors the voltageof the battery pack 14.

At block 1215, the processor 1105 controls the load bank switch 1135 toconnect the battery pack 14 to a second load of the load bank 1130 suchthat the battery pack 14 applies a second discharge current (e.g., oneamp). The battery pack 14 remains connected to this load for a timeperiod (e.g., five seconds). During this time, the processor 1105monitors the voltage of the battery pack 14.

As indicated by blocks 1220 and 1225, blocks 1210 and 1215 are repeateda number of times (e.g., twice), and the voltage of the battery pack 14continues to be monitored. After blocks 1210 and 1215 are repeated (inother words, after blocks 1210 and 1215 have been executed three timesin total), at block 1230, the processor 1105 resets a variable N to zerosuch that the next time the method 1200 is executed, the blocks 1210 and1215 will be executed once and then repeated the number of times more(in other words, blocks 1210 and 1215 are executed three times each timethe method 1200 is executed).

At block 1235, the processor 1105 determines how much the voltage of thebattery pack 14 varied from when the battery pack 14 was connected tothe first load compared to when the battery pack 14 was connected to thesecond load. A large variance in the voltage of the battery pack 14indicates a higher DC internal resistance and a less healthy batterypack 14 than does a smaller variance. In other words, the less thevoltage of the battery pack 14 varied when the loads were switched, thehealthier the battery pack 14.

The variance in voltage may be compared to a variance in the voltage ofthe battery pack 14 when the battery pack 14 was manufactured. Anincrease in the variance in the voltage of the battery pack 14 from thetime of manufacture beyond a predetermined threshold (e.g., a 50%increase) may indicate that the battery pack 14 should be replaced orused only for lower power applications.

FIG. 13 illustrates a graph that shows exemplary results of the method1200 being executed on an exemplary 18V battery pack. In FIG. 13, thex-axis of the graph represents time in seconds. The lower signal on thegraph represents a discharge current 1305 of the battery pack in amps,and the upper signal represents a battery pack voltage 1310 in volts.

As shown in FIG. 13, the discharge current 1305 includes a number (e.g.,six) of time period (e.g., five second) intervals that alternate betweenthe first discharge current (e.g., ten amps) and the second dischargecurrent (e.g., one amp). As shown in FIG. 13, the battery pack voltage1310 varies as the discharge current 1305 of the battery pack 14 varies.As mentioned above, the amount of variance of the battery pack voltage1310 indicates the health of the battery pack 14.

In some embodiments, the method 1200 is executed by the processor 1105of the charger 1005 before charging of the battery pack 14. In otherembodiments, the method 1200 is executed at other times (for example,after the battery pack 14 has been charged for a predetermined time,after the battery pack 14 has been charged to a predetermined capacity,after the battery pack 14 has been fully charged, etc.).

After executing the method 1200 to determine the health of the batterypack 14, the processor 1105 may control the LEDs 1115 to illuminate toindicate the health of the battery pack 14. For example, in someembodiments, the LEDs 1115 may include a green LED, a yellow LED, and ared LED. In such embodiments, the processor 1105 may illuminate thegreen LED when the battery health is in a first range indicating goodhealth (for example, when the DC internal resistance is within 20% ofits initial DC internal resistance). The processor 1105 may illuminatethe red LED when the battery health is in a second range indicating poorhealth (for example, when the DC internal resistance has increased by50% or more of its initial DC internal resistance). The processor 1105may illuminate the yellow LED when the battery health is in a thirdrange between the first range and the second range. It should beunderstood that these ranges are merely exemplary and may be differentin other embodiments.

In alternate embodiments, the LEDs 1115 may include a plurality ofsingle-color LEDs that the processor 1105 controls to illuminate in asimilar manner as described above with respect to the green, yellow, andred LEDs. For example, in an embodiment with five single-color LEDs, theprocessor 1105 may illuminate all five LEDs when the battery pack 14 isin good health and may only illuminate one single-color LED when thebattery pack 14 is in poor health. Accordingly, the charger 1005 maydetermine and notify a user (through the LEDs 1115) when the batterypack 14 is in poor health.

In some embodiments, the charger 1005 includes a wireless communicationcontroller to communicate with an external device (e.g., a smart phone).In such embodiments, the wireless communication controller and theexternal device may be similar to those disclosed in U.S. PatentApplication Publication No. 2016/0342151.

In some embodiments, the charger 1005 provides information to theexternal device using the wireless communication controller after thehealth of the battery pack 14 (i.e., the DC internal resistance of thebattery pack 14) is determined. For example, when the DC internalresistance of the battery pack 14 increases above a predeterminedthreshold (i.e., when the measured variance in voltage during loadswitching increases above a predetermined threshold), the charger 1005may provide a recommendation to the external device that the batterypack 14 should be replaced or that the battery pack 14 should only beused to power low-demand devices (e.g., light duty tools and devicessuch as a work light). In turn, the external device communicates thisinformation to a user (e.g., displays this recommendation such that itis viewable by the user).

As mentioned above, such a recommendation may increase the useful lifeof the battery pack 14 and/or may increase the performance of devices(e.g., high-demand devices) by informing the user of an ideal use forthe battery pack 14 based on its health. Thus, newer battery packs withgood health may be used to power high-demand devices while older batterypacks with diminished health are more appropriate to power low-demanddevices.

While the charger 1005 is described as including the wirelesscommunication controller above, in some embodiments, the battery pack 14and/or the nailing device 10 may include a wireless communicationcontroller to communicate with the external device. In such embodiments,the processor 1105 of the charger 1005 may communicate with the batterypack 14 such that the battery pack 14 stores battery health informationin its memory. The battery pack 14 may then communicate the batteryhealth information to the external device. In alternate embodiments, thebattery pack 14 may communicate battery health information to a powertool/device when coupled to the power tool/device, and the powertool/device, in turn, may communicate the battery health information toan external device.

It should be understood that each block diagram is simplified and inaccordance with the illustrated exemplary embodiment. The components andconnections illustrated in the block diagrams are exemplary, andadditional or fewer components/connections may be provided. For example,in FIG. 3A, the device 10 may include additional circuitry (for example,circuitry between the second switch 335 and the motor 22 to drive themotor 22 in a predetermined manner). Similarly, the flowcharts aresimplified and exemplary, and additional or fewer steps may be provided.

Although the invention has been described in detail with reference tocertain preferred embodiments, variations and modifications exist withinthe scope and spirit of one or more independent aspects of the inventionas described.

We claim:
 1. A battery pack comprising: a housing configured to beremovably coupled to and supported by a device configured to receivepower from the battery pack; a plurality of battery cells supported inthe housing, the plurality of battery cells including a first batterycell having a first physical size and a second battery cell having asecond physical size different than the first physical size; and aterminal configured to be electrically connected to the first batterycell and the second battery cell, wherein power is transferrable, viathe terminal, from the first battery cell and the second battery cell tothe device.
 2. The battery pack of claim 1, wherein the first physicalsize and the second physical size include at least one of a diameter ofa respective battery cell and a length of the respective battery cell.3. The battery pack of claim 1, wherein the housing includes: a baseconfigured to house the first battery cell, wherein the first physicalsize of the first battery cell is larger than the second physical sizeof the second battery cell; and a stem coupled to and extending from thebase, wherein the stem is configured to be inserted into a batteryreceptacle of the device and wherein the stem is configured to house thesecond battery cell.
 4. The battery pack of claim 3, wherein the stem isconfigured to house a plurality of the second battery cells, the secondbattery cells having a first diameter of eighteen millimeters; andwherein the base is configured to house a plurality of the first batterycells, the first battery cells having a second diameter of greater thaneighteen millimeters.
 5. The battery pack of claim 1, wherein the firstphysical size of the first battery cell is larger than the secondphysical size of the second battery cell; wherein at least two rows ofthe first battery cells are included in the housing; and wherein a rowof the second battery cells are positioned in the housing at least oneof (i) in between the at least two rows of the first battery cells and(ii) along a bottom of a base of the housing underneath one of the atleast two rows of the first battery cells.
 6. The battery pack of claim1, wherein the first battery cell and the second battery cell havesubstantially the same nominal voltage.
 7. The battery pack of claim 1,wherein the plurality of battery cells includes a plurality of the firstbattery cells and a plurality of the second battery cells; wherein eachone of the first battery cells is electrically connectable in parallelwith a respective one of the second battery cells to form a plurality ofparallel-connected battery cells of different physical size; and whereinthe plurality of parallel-connected battery cells of different physicalsize are electrically connectable in series to the terminal.
 8. Thebattery pack of claim 1, further comprising an electronic processorconfigured to control one or more switches, wherein the one or moreswitches is configured to electrically disconnect at least one of thefirst battery cell and the second battery cell from the terminal.
 9. Thebattery pack of claim 8, further comprising a sensor configured to beelectrically connected to the electronic processor, wherein theelectronic processor is configured to: determine at least one of anambient condition of the battery pack and an operational condition ofthe battery pack; and control the one or more switches to electricallydisconnect the at least one of the first battery cell and the secondbattery cell from the terminal based on the at least one of the ambientcondition and the operational condition.
 10. The battery pack of claim1, wherein the first battery cell has a first characteristic and thesecond battery cell has a second characteristic different than the firstcharacteristic, the first characteristic and the second characteristicbeing at least one of a shape, a chemistry, and an operationalcharacteristic.
 11. The battery pack of claim 1, wherein the deviceincludes a power tool.
 12. The battery pack of claim 1, wherein theplurality of battery cells are electrically connectable to each othervia conductive straps that are laser welded to battery cell terminals ofthe plurality of battery cells.
 13. A method of powering a device, themethod comprising: providing a battery pack including a housingconfigured to be removably connected to and supported by the deviceconfigured to receive power from the battery pack, and a plurality ofbattery cells supported in the housing, the plurality of battery cellsincluding a first battery cell having a first physical size and a secondbattery cell having a second physical size different than the firstphysical size; and transferring, via a terminal of the battery packconfigured to be electrically connected to the first battery cell andthe second battery cell, power from the first battery cell and thesecond battery cell to the device.
 14. The method of claim 13, whereinthe first physical size and the second physical size include at leastone of a diameter of a respective battery cell and a length of therespective battery cell.
 15. The method of claim 13, wherein the firstbattery cell and the second battery cell have substantially the samenominal voltage.
 16. The method of claim 13, further comprisingcontrolling, with an electronic processor, one or more switches, whereinthe one or more switches is configured to electrically disconnect atleast one of the first battery cell and the second battery cell from theterminal.
 17. The method of claim 16, wherein the electronic processoris configured to: receive a signal from a sensor of the battery pack;determine at least one of an ambient condition of the battery pack andan operational condition of the battery pack based on the signal; andcontrol the one or more switches to electrically disconnect the at leastone of the first battery cell and the second battery cell from theterminal based on the at least one of the ambient condition and theoperational condition.
 18. A battery pack comprising: a housing; aplurality of battery cells supported in the housing, the plurality ofbattery cells including a first battery cell having a firstcharacteristic and a second battery cell having a second characteristicdifferent than the first characteristic, the first characteristic andthe second characteristic being at least one of a physical size, ashape, a chemistry, and an operational characteristic; and a terminalelectrically connected to the first battery cell and the second batterycell.
 19. The battery pack of claim 18, wherein the operationalcharacteristic is at least one of an Ampere-hour capacity and atemperature performance characteristic.
 20. The battery pack of claim18, wherein the first battery cell and the second battery cell havesubstantially the same nominal voltage.